1. Technical Field
This invention relates to a piezoelectric head inspection device and a droplet jetting device, and more particularly to an inspection device and a droplet jetting device which inspect for causes of defective ejections from nozzles of piezoelectric heads.
2. Related Art
Heretofore, in a piezoelectric head which employs piezoelectric elements (piezoactuators or the like), pressure is applied in pressure chambers by the application of voltages to the piezoelectric elements, and ink drops are ejected from nozzles.
Now, when a bubble enters through an ink supply channel, an ejection failure occurs at the nozzle. In order to pre-emptively prevent this failure, an operation of maintenance by suction is necessary. Further, if foreign matter, such as paper dust or the like, or congealed ink or the like adheres to a nozzle face, surface tension is altered and ejection direction defects occur. Therefore, an operation of maintenance by wiping is necessary.
In a case in which it is not possible to detect occurrences of defective ejections, such as ejection failures, ejection direction defects and the like, it is necessary to perform periodic maintenance. Consequently, there is a problem in that this results in wastages of time and ink. Further, as mentioned above, maintenance operations include suction and wiping. While suction is effective for bubble removal, it is not very effective for removal of foreign matter from the nozzle face. Therefore, in a case in which it is not possible to detect causes of defective ejections, there is a risk of maintenance operations being purposeless.
Accordingly, as a method for inspecting for ejection failures, a nozzle inspection method has been known which detects ejection failures from changes in resonance points of piezoelectric elements by frequency-sweeping.
Further, as a device for inspecting for causes of defective ejections such as ejection failures, ejection direction defects and the like, a droplet ejection device has been known in which oscillations at a characteristic frequency are generated by an oscillation circuit, and which detects ejection failures, jetting irregularities and the like from changes in the frequency.
However, with the above-described technologies, it is necessary to implement oscillations by frequency-sweeping or an oscillation circuit or the like. Therefore, it is difficult to incorporate equipment for inspecting a piezoelectric head into a droplet jetting device, and a complicated structure results.